The glands of the oral cavity (the salivary glands)
The glands which secrete the saliva are divided into two groups: the numerous small glands in the walls of the oral cavity and the three large (paired) salivary glands.
The latter are the parotid, the submaxillary, and the sublingual. They possess excretory ducts of varying lengths, which empty into the oral cavity.
The parotid, the largest oral salivary gland, is of a flattened irregular triangular shape and is situated in front of the external ear in the parotideo-masseteric region and partly also in the retromandibular fossa. Its slightly convex external surface is covered by the skin, the prolongations of the platysma (and risorius), and the parotideo-masseteric fascia, while the slightly concave internal surface rests chiefly upon the masseter.
The anterior portion of the gland is much the thinner, and the anterior somewhat concave margin is slightly beveled and lies upon the external surface of the masseter. The inferior margin is directed somewhat posteriorly, so that it forms an acute angle with the anterior margin, this tip of the gland being situated in the neck and sometimes extending as far down as the sub-maxillary gland. The inferior and posterior margin rests upon the anterior margin of the sternocleidomastoid and the superior margin is generally irregular and is in relation with the zygoma and the external auditory meatus.
The posterior portion of the gland, situated behind the posterior margin of the masseter, covers the outer surface of the ramus of the lower jaw, and its retromandibular process extends behind the ramus to come into relation with the internal pterygoid, the posterior belly of the digastric, and the muscles coming from the styloid process. This glandular process usually also reaches as far as the internal carotid artery and the internal jugular vein.
The parotid gland is traversed by the branches of the facial nerve which are situated nearer the internal than the external surface and form the parotid plexus within its substance. The upper branches of the external carotid, particularly the superficial temporal and some of its ramifications, as well as the posterior facial (temporo-maxillary) vein, may also be more or less enveloped by the lobules of the gland.
The duct of the parotid gland, the parotid duct (ductus Stenoni), appears at the upper portion of the anterior margin of the gland and passes almost transversely across the masseter, bends just in front of its anterior margin, and passes through the fatty tissue in this situation (the buccal fat pad) and the buccinator to the buccal mucous membrane which it perforates obliquely. The orifice of the duct is in the vestibulum oris and appears as a rounded slit opposite the upper second molar tooth.
Several small conglomerations of lobules are very frequently observed about the parotid duct and are known as the accessory parotid gland. The parotid gland is grayish-yellow or yellowish-brown in color and seems distinctly lobulated like the other salivary glands, but the lobules are quite small; at the margins of the gland they are frequently isolated, but throughout the chief mass of the structure they are arranged compactly.
The submaxillary gland is a rounded structure, the long axis of which is in the sagittal plane. It is found in the neck, in the submaxillary region, immediately beneath the platysma and the cervical fascia, the latter structure forming a fibrous capsule for the gland.
The greater portion of the submaxillary gland lies beneath the mylohyoid muscle in the space between the angle of the jaw and the two bellies of the digastric. It also borders upon the stylohyoid and styloglossus, and its internal surface is in relation with the hyoglossus.
The external maxillary (facial) artery and its accompanying vein run in the immediate vicinity.
The upper margin of the gland rests against the body of the jaw and is lodged in a depression which is not always distinct, the submaxillary depression.
The gland is yellowish-white in color and is distinctly lobulated, the lobules being considerably larger than those of the parotid. A thin and markedly flattened glandular process extends upward between the internal pterygoid and the mylohyoid to the sublingual gland and accompanies the secretory duct for some distance.
The submaxillary duct (ductus Whartoni) is the size of an ordinary quill; it is given off from the upper part of the gland and runs above the mylohyoid, between that muscle and the mucous membrane of the floor of the mouth (or the sublingual gland), passing from behind forward and inward and producing the sublingual fold. The orifice in the oral cavity is situated on the sublingual caruncle beside the frenulum beneath the tip of the tongue
The sublingual gland is an elongated flattened structure with its long axis in the sagittal plane, and may be distinctly seen beneath the mucous membrane of the floor of the mouth when the tip of the tongue is raised. The external border is lodged in a depression in the inferior maxillary bone, the sublingual depression, and the posterior margin is in relation with the submaxillary gland, the internal margin with the genioglossus, and its lower surface rests upon the mylohyoid. In the immediate vicinity of the gland are the sublingual artery and the lingual nerve.
The gland is white or light-gray in color and has distinct lobules which are smaller than those of the submaxillary. It is the smallest of the three salivary glands and is not so compactly arranged, frequently consisting of several glandular masses which are only loosely connected.
It does not possess a common duct, but the secretion from the distinctly separated glandular components is poured out through ten or twelve ducts known as the lesser sublingual ducts (ducts of Rivinus), which empty immediately into the oral cavity by a number of small punctiform orifices in the region of the sublingual fold. The anterior portion of the gland, however, frequently gives off a somewhat larger duct, which is known as the greater sublingual duct (duct of Bartholin), and this either empties independently at the sublingual caruncle beside the submaxillary duct or pours its secretion into the latter structure immediately before its termination. Both the submaxillary and the sublingual glands consequently empty into the oral cavity, while the orifice of the duct of the parotid gland is situated in the vestibulum oris.
The tube there is an inconstant elevation caused by the underlying levator veli palatini, and a rather distinct fold, the salpingopharyngeal fold, extends from the torus tubarius to the lateral pharyngeal wall, where it gradually disappears, and above and behind the torus tubarius the pharyngeal fornix upon either side forms a narrow blind pocket, the pharyngeal recess (cavity of Rosenmuller). Between the two tubal orifices and actually in the roof of the pharynx is situated the pharyngeal tonsil, a lymphatic structure which is usually distinct only in children.
The oral portion of the pharynx communicates with the oral cavity through the isthmus of the fauces, the boundary being marked by the pharyngopalatine arches. It is the narrowest portion of the pharynx and presents no special structures, except a fold of mucous membrane, the pharyngo- epiglottic fold, which passes from the lateral margin of the epiglottis to the outer pharyngeal wall and separates the oropharynx from the laryngopharynx.
The laryngeal portion of the pharynx is the only portion which has an extensive anterior wall. It lies behind the larynx, the posterior wall of which is distinctly visible through the thin pharyngeal mucous membrane, so that there may be recognized a median elevation produced by the plate of the cricoid cartilage (and the arytenoid cartilages) and two deep lateral depressions which correspond to those between the cricoid and arytenoid cartilages internally, and the posterior surface of the thyreoid cartilage externally. These lateral depressions are termed the piriform recesses and present a fold of mucous membrane, the fold for the laryngeal nerve, which passes obliquely from above downward and from without inward, and contains the superior laryngeal nerve. In the laryngopharynx is also situated the entrance to the larynx or aditus laryngis.
The pharyngeal wall consists of a mucous membrane, of a submucous layer, and of a muscular coat. The mucous membrane is red and smooth, rather thin in its inferior portion, and contains small mucous pharyngeal glands, especially abundant in the upper portion.
In this upper portion the musculature is absent for a distance of about two centimeters, and the submucosa in this situation forms a strong fibrous membrane which is designated as the pharyngobasilar fascia (pharyngeal aponeurosis) and inserts into the base of the skull.
The muscular coat of the pharynx is found in the lateral and posterior walls with the exception of the uppermost pftrtion. It consists practically of circular fibers which meet in the median line, the pharyngeal raphe, and partly interlace, and in it there may be recognized three flat, thin muscles situated one above the other and known as the constrictors of the pharynx.
The constrictor pharyngis superior (cephalo pharyngeus) is composed of four portions, named according to their origins, which unite to form a single muscular lamina in the lateral wall of the pharynx. The uppermost fasciculi coming from the hamular process and the contiguous portion of the internal plate of the pterygoid process are designated as the pterygopharyngeus; the next fasciculi are those of the buccopharyngeus and represent the backward continuation of the buccinator, from which ihey: are separated by TFe pterygomandibular raphe; the mylo pharyngeus comes from the posterior part of the mylohyoid line of the mandible; and the small glossopharyngeus, the most inferior portion, originates in the lingual musculature, chiefly from the fasciculi of the transversus linguae.
The constrictor pharyngeus medius (hyo pharyngeus) arises from the lesser (chondro pharyngeus) and the greater (cerato pharyngeus) cornua of the hyoid bone. Only the middle fasciculi pass horizontally to meet in the median raphe, both the upper and the lower fasciculi running obliquely (upward or downward as the case may be) and consequently meeting in the raphe at an acute angle. As a result of this insertion the upper apex of the muscle covers the constrictor pharyngis superior, while the greater portion of the muscle is itself covered by the constrictor pharyngis inferior.
The constrictor pharyngis inferior (laryngo pharyngeus) is the largest and much the longest of the pharyngeal constrictors. It consists of two portions which are separated only at their origins. The larger superior portion, known as the thyreo pharyngeus, arises from the entire outer surface of the plate of the thyreoid cartilage, extending from the superior to the inferior cornu; the smaller inferior portion, termed the crico pharyngeus, comes from the outer surface of the ring of the cricoid cartilage. The fibers of this latter portion run almost horizontally; the fibers of the upper portion, on the contrary, pass obliquely upward (the uppermost ones rather sharply) and form an acute angle, the apex of which is directed upward and conceals the greater portion of the constrictor medius.
The stylo pharyngeus acts as an elevator of the pharynx. It arises from the inner side of the styloid process of the temporal bone at the side of and behind the pharynx, and forms a slender, slightly flattened muscle which broadens as it approaches its insertion. The majority of the fibers pass into the lateral wall of the pharynx between the superior and inferior constrictors, with which they interlace, especially with the latter. A few fasciculi also pass to the lateral margin of the epiglottis and to the upper margin of the thyreoid cartilage.
The diaphragm and the pylorus of the stomach are drawn upward and the stomach is rather strongly contracted.
The salpingo pharyngeus is an inconstant muscle situated in the fold of the same name, which arises from the cartilaginous end of the tuba auditiva (Eustachian tube) and passes to the lateral wall of the pharynx.
The pharyngeal muscles are innervated through the pharyngeal plexus (see Neurology).
Human Anatomy (1909) by DR. Johannes Sobotta (1869-1945) Professor of Anatomy in the university of Wurzburg